Blenderkit addon - Error while trying to enable the addon in Blender 2.9
For all who might have the same problem, I found a solution thanks to the addon developers, I guess there was a conflict between several downloaded versions of blender, so to fix the issue, I went to the following path
C:\Users[Your Username]\AppData\Roaming\Blender foundation
I deleted the blender foundation folder and restarted blender and now I was able to enable the addon again
make sure to show hidden files in order to see App Data folder.